Mechanical fasteners are used to connect or attach. Bone screws and suture anchors are used pervasively in the treatment of fractured bones and in wound closures and during the course of surgical procedures to secure and/or attach things. During the course of a surgical procedure, a suture is typically anchored to enable it to better perform its function of attaching or securing. That is, one end of a suture is attached to some substrate and the other end is used to secure or attach a desired object to the substrate. In a typical example, a suture is used to attach a tendon to a bone that it has become detached from. Sutures are also used to attach or secure muscles, ligaments, tissue and prostheses during the course of a surgical procedure. Screws are generally used to secure surgical plates to provide rigid fixation of bones.
Numerous devices such as, inter alia bone screws, staples, anchors, and rivets are used to anchor sutures. Often these devices are inserted into a hole formed in a substrate, such as, a bone, and secured within the hole through barbs, fins, ribs, or some other securing mechanism which "digs into" or causes friction with the surrounding bone. Examples of such devices are described in U.S. Pat. No. 4,898,156; U.S. Pat. No. 5,037,422; U.S. Pat. No. 5,217,486; and U.S. Pat. No. 5,486,197. These devices suffer from various drawbacks.
One drawback is that these devices are difficult to use. Typically, a suture is attached to these devices by threading the suture through a hole (i.e., through-threading) and tying a knot to secure the suture. This threading operation is typically very difficult to perform during a surgical operation and may take as long as fifteen minutes to accomplish. Alternatively, in some cases a suture is preattached to the anchor. Nevertheless, if the suture breaks during use the entire anchor may have to be removed in order to reattach a suture. And, removal of these conventional anchors is difficult and traumatic because installation is typically irreversible. That is, once they are inserted into a substrate, they cannot be removed without causing damage to the substrate.
Further, because these devices operate by "digging" into or creating friction with the surrounding substrate, they require a sufficiently thick substrate to effectively anchor. Therefore, although these devices may provide an effective anchor in a relatively thick bone (e.g., the knee, shoulder, elbow, etc.) they are much less effective in areas where the bone is thinner (e.g., craniofacial, metatarsals, metacarpals). Further, these devices may extend well below the surface of the bone, and thus provide a path for suture chafe.
Moreover, problems with difficulty of use extend to conventional bone screws as well. For instance, although a conventional bone screw may be installed and removed, they typically do not provide for attachment of sutures or for secure self-retaining attachment of the screwdriver to the screw. More specifically, if a suture is to be attached to a conventional bone screw, it will typically have to be threaded under the screw head or through a hole that the bone screw has been retrofitted with. Additionally, bone screws are often difficult to install in the operating room. That is, bone screws are generally inserted into predrilled holes, and have to be held in place until the threads of the screw engage with the sides of the predrilled hole. As such, conventional bone screws require pre drilling and a capture device be used in the operating room to form a hole and place a bone screw. Thus, there is a necessity of a capture device in the operating room and an additional sterilization procedure.
Further, the act of holding a bone screw can be difficult when the bone screw is being inserted into a confined area. Although there are some methods of holding a bone screw to the driver these conventional methods of holding the bone screw to the driver are often unsatisfactory. One conventional method involves the use of a clasp structure to hold the bone screw to the driver as shown in FIG. 8a & 8b. While this method may be effective in certain circumstances, the clasp structure is generally cumbersome and obscures the view of the hole and screw making it difficult to start the screw in a bloody environment or confined space. Another conventional method involves using a flared driver blade to establish a friction fit between the driver blade and a slot on the bone screw head as shown in FIG. 9a & 9b. Nevertheless, this configuration has a drawback as well in that the strength of the holding force varies depending on the strength of the force used to establish the friction fit. It is difficult to gauge the strength of the holding force and thus, the hold is often too weak or too strong. If the hold is too weak, the screw may fall off If the hold is too strong, a strong force may be necessary to disengage the screw from the driver. If this force exceeds the force of the holding bone it may strip the screw from its hole or fracture additional bone.
There are also applications in which the use of conventional anchors is inappropriate or in which it is difficult to find a suitable substrate to use for conventional anchors or in which anchor size is inappropriate. For example, during installation of a piece of surgical hardware, such as a cardiac pacemaker or surgical prosthesis there are typically certain locations on the hardware that need to be secured to adjacent structures or where it would be desirable to have a point of attachment. Examples include: optical implants, dental implants or extraction devices, cardiac pacemakers, catheter tubes, drainage tubes, general orthopedic implants, bladder suspensions devices, etc. Nevertheless, there is often no rigid substrate in the vicinity that is suitable for anchoring. Moreover, it is undesirable to have through holes, raised surfaces, or extensions on the surfaces of these devices for both clinical and cosmetic reasons.
Therefore, the inventor has recognized that a need has arisen for new self-retaining mechanical fasteners, such as self-retaining screws, self-retaining bone screws, suture anchors and more particularly a track and a process for fabricating the track into general hardware that overcomes the drawbacks discussed above.